﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace WebSite
{
    /// <summary>
    /// vCode 的摘要说明
    /// </summary>
    public class vCode : IHttpHandler, System.Web.SessionState.IRequiresSessionState
    {
        string _vcode = string.Empty;
        public void ProcessRequest( HttpContext context )
        {
            context.Response.Buffer = true;
            context.Response.ExpiresAbsolute = DateTime.Now.AddSeconds( -1 );
            context.Response.Expires = -1;
            context.Response.CacheControl = "no-cache";

            //Random rand = new Random();
            //_vcode = rand.Next(1000, 9999).ToString();

            this.buildCodeImage( context );
        }

        private void buildCodeImage( HttpContext context )
        {
            string chkCode = string.Empty;
            //颜色列表，用于验证码、噪线、噪点 
            Color[] color = { Color.Black, Color.Blue };
            //字体列表，用于验证码 
            string[] font = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" };
            //验证码的字符集，去掉了一些容易混淆的字符 
            char[] character = { '2', '3', '4', '5', '6', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };
            Random rnd = new Random();
            //生成验证码字符串 
            for (int i = 0; i < 4; i++)
            {
                chkCode += character[rnd.Next( character.Length )];
            }
            context.Session["VCODE"] = chkCode;
            Bitmap bmp = new Bitmap( 60, 20 );
            Graphics g = Graphics.FromImage( bmp );
            g.Clear( Color.White );
            //画噪线 
            //for (int i = 0; i < 3; i++)
            //{
            //    int x1 = rnd.Next( 20 );
            //    int y1 = rnd.Next( 10 );
            //    int x2 = rnd.Next( 20 );
            //    int y2 = rnd.Next( 40 );
            //    Color clr = color[rnd.Next( color.Length )];
            //    g.DrawLine( new Pen( clr ), x1, y1, x2, y2 );
            //}
            //画验证码字符串 
            for (int i = 0; i < chkCode.Length; i++)
            {
                string fnt = font[rnd.Next( font.Length )];
                Font ft = new Font( fnt, 12 );
                Color clr = color[rnd.Next( color.Length )];
                g.DrawString( chkCode[i].ToString(), ft, new SolidBrush( clr ), (float)i * 13 + 2, (float)2 );
            }
            //画噪点 
            for (int i = 0; i < 100; i++)
            {
                int x = rnd.Next( bmp.Width );
                int y = rnd.Next( bmp.Height );
                Color clr = color[rnd.Next( color.Length )];
                bmp.SetPixel( x, y, clr );
            }
            //清除该页输出缓存，设置该页无缓存 
            context.Response.Buffer = true;
            context.Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds( 0 );
            context.Response.Expires = 0;
            context.Response.CacheControl = "no-cache";
            context.Response.AppendHeader( "Pragma", "No-Cache" );
            //将验证码图片写入内存流，并将其以 "image/Png" 格式输出 
            MemoryStream ms = new MemoryStream();
            try
            {
                bmp.Save( ms, ImageFormat.Png );
                context.Response.ClearContent();
                context.Response.ContentType = "image/Png";
                context.Response.BinaryWrite( ms.ToArray() );
            }
            finally
            {
                //显式释放资源 
                bmp.Dispose();
                g.Dispose();
            }
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}